The present invention relates to the modifications of dip molding technology, such as used in production of medical gloves and condoms, in order to adapt the established process for automated manufacturing of thin-walled elastomeric sleeves with both ends opened and finished with rolled beads.
Up until now the art of automated and semi-automated production of thin-walled elastomeric sleeves of complex shapes with both finished ends has not been developed. Small batches of sleeves from latex and like materials with rolled beads at both ends have been manufactured by several companies, however, the employed process is excessively labor intensive and therefore expensive. The technique presently used relies largely on manual labor, which prevents large scale production.
Meanwhile the demand for this kind of sleeves is rather high, particularly in the healthcare field where exists an urgent need for resilient water-resistant disposable protective sleeves. This demand is reflected in a number of United States patents, particularly the U.S. Pat. No. 6,276,364, issued on Aug. 21, 2001. U.S. Pat. No. 5,143,762 and U.S. Pat. No. 5,592,953 further confirm the necessity for low cost disposable sleeves.
Nowadays the art of producing thin-walled natural and synthetic rubber articles is perfectly developed and employs a very well established technique called dip molding. This technique is used primarily for manufacturing natural and synthetic rubber gloves, condoms, finger cots and like objects. The dip molding process is largely automated and is performed by continuous mechanical lines whereon sets of special formers are moved sequentially from one stage to the next. Along the way the formers are dipped first in coagulant, then in elastomeric suspension also passing on their way leaching and drying intermediate stages. After drying coagulum layer covering the formers turns into natural or synthetic rubber. After the drying is completed, most types of production are taken through the stage of bead rolling. We can distinguish two major types of production lines: automated and semi-automated (AKA “batchtype”). On automated lines beading is performed by special brushes whereas on batch lines—in most cases—manually. Eventually the formers pass the curing oven, after which the finished rubber articles are stripped from formers.
Automation of manufacturing thin-walled sleeves of latex and like elastomeric materials is prevented by the contradiction inherent to the nature of the dip molding technique whereby it is required that a former is dipped first in coagulant and then in suspension (normally aqueous) of natural or synthetic latex, which causes the lower end of the former to be covered by latex coagulum, which after subsequent drying and curing turns into thin-walled synthetic or natural rubber article. Inevitably the lower end of a former in such a process has to be enclosed in coagulum and—after curing—in thin layer of rubber. In order to produce sleeves, opened at both ends and having rolled beads at both ends, the rubber encasements are cut off the lower ends of the formers and stripped from the formers before the sleeves produced in this manner are vulcanized. Employing such sequence enables the raw rubber to stick to itself and form a bead. Once the bead rolling is completed at both ends, the dry latex article can be finally cured and stripped from the former. Such technique, however, is very involved and labor intensive, which drives up the cost of elastomeric sleeves and hinders large scale manufacturing, required for production low cost disposable devices.
A number of patents, particularly U.S. Pat. No. 3,978,187 suggest modifications of dip molding techniques which could allow automation of production thin-walled elastomeric sleeves, however these methods drastically break away from the universally adapted dip molding technology, therefore requiring dramatic and expensive restructuring of the industry in order to produce the sleeves. Besides the method suggested in the U.S. Pat. No. 3,978,187 does not provide for easy bead rolling.
The invention proposed herein prescribes a set of simple and inexpensive modifications to the existing technology which allows to avoid the inherent contradictions of the presently accepted methods and to implement automated and semi-automated (batch) production of thin-walled elastomeric sleeves of complex shapes with beads at both ends. The method described hereinafter is derived from and is based upon established standard manufacturing procedures, thus providing inexpensive transition from manufacturing gloves or condoms to producing thin-walled elastomeric sleeves. The objective of this invention is to provide inexpensive means of mass production of synthetic and natural rubber sleeves employing existing manufacturing facilities.